Instructor, Neurology & Neurological Sciences
Honors & Awards
Dean of Medicine's Postdoctoral Fellowship, Stanford University (2018)
PhD, McGill University, Neuroscience (2016)
Master of Science, McGill University, Psychology (2011)
Bachelor of Science, Dalhousie University, Neuroscience and Biology (2008)
Current Research and Scholarly Interests
Single-cell transcriptomic profiling of immune cells in Alzheimer's disease brain
Alzheimer's disease, Parkinson's disease and multiple sclerosis biomarkers
Alzheimer’s disease experimental therapeutics
PET imaging of TREM1 identifies CNS-infiltrating myeloid cells in a mouse model of multiple sclerosis.
Science translational medicine
2023; 15 (702): eabm6267
Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS) that causes substantial morbidity and diminished quality of life. Evidence highlights the central role of myeloid lineage cells in the initiation and progression of MS. However, existing imaging strategies for detecting myeloid cells in the CNS cannot distinguish between beneficial and harmful immune responses. Thus, imaging strategies that specifically identify myeloid cells and their activation states are critical for MS disease staging and monitoring of therapeutic responses. We hypothesized that positron emission tomography (PET) imaging of triggering receptor expressed on myeloid cells 1 (TREM1) could be used to monitor deleterious innate immune responses and disease progression in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. We first validated TREM1 as a specific marker of proinflammatory, CNS-infiltrating, peripheral myeloid cells in mice with EAE. We show that the 64Cu-radiolabeled TREM1 antibody-based PET tracer monitored active disease with 14- to 17-fold higher sensitivity than translocator protein 18 kDa (TSPO)-PET imaging, the established approach for detecting neuroinflammation in vivo. We illustrate the therapeutic potential of attenuating TREM1 signaling both genetically and pharmacologically in the EAE mice and show that TREM1-PET imaging detected responses to an FDA-approved MS therapy with siponimod (BAF312) in these animals. Last, we observed TREM1+ cells in clinical brain biopsy samples from two treatment-naïve patients with MS but not in healthy control brain tissue. Thus, TREM1-PET imaging has potential for aiding in the diagnosis of MS and monitoring of therapeutic responses to drug treatment.
View details for DOI 10.1126/scitranslmed.abm6267
View details for PubMedID 37379371
Performance of a fully-automated Lumipulse plasma phospho-tau181 assay for Alzheimer's disease.
Alzheimer's research & therapy
2022; 14 (1): 172
BACKGROUND: The recent promise of disease-modifying therapies for Alzheimer's disease (AD) has reinforced the need for accurate biomarkers for early disease detection, diagnosis and treatment monitoring. Advances in the development of novel blood-based biomarkers for AD have revealed that plasma levels of tau phosphorylated at various residues are specific and sensitive to AD dementia. However, the currently available tests have shortcomings in access, throughput, and scalability that limit widespread implementation.METHODS: We evaluated the diagnostic and prognostic performance of a high-throughput and fully-automated Lumipulse plasma p-tau181 assay for the detection of AD. Plasma from older clinically unimpaired individuals (CU, n = 463) and patients with mild cognitive impairment (MCI, n = 107) or AD dementia (n = 78) were obtained from the longitudinal Stanford University Alzheimer's Disease Research Center (ADRC) and the Stanford Aging and Memory Study (SAMS) cohorts. We evaluated the discriminative accuracy of plasma p-tau181 for clinical AD diagnosis, association with amyloid beta peptides and p-tau181 concentrations in CSF, association with amyloid positron emission tomography (PET), and ability to predict longitudinal cognitive and functional change.RESULTS: The assay showed robust performance in differentiating AD from control participants (AUC 0.959, CI: 0.912 to 0.990), and was strongly associated with CSF p-tau181, CSF Abeta42/Abeta40 ratio, and amyloid-PET global SUVRs. Associations between plasma p-tau181 with CSF biomarkers were significant when examined separately in Abeta+ and Abeta- groups. Plasma p-tau181 significantly increased over time in CU and AD diagnostic groups. After controlling for clinical diagnosis, age, sex, and education, baseline plasma p-tau181 predicted change in MoCA overall and change in CDR Sum of Boxes in the AD group over follow-up of up to 5 years.CONCLUSIONS: This fully-automated and available blood-based biomarker assay therefore may be useful for early detection, diagnosis, prognosis, and treatment monitoring of AD.
View details for DOI 10.1186/s13195-022-01116-2
View details for PubMedID 36371232
alpha-synuclein seed amplification in CSF and brain from patients with different brain distributions of pathological alpha-synuclein in the context of co-pathology and non-LBD diagnoses.
Annals of neurology
OBJECTIVE: To determine the sensitivity and specificity of alpha-synuclein seed amplification assay (alphaSyn-SAA) in antemortem and postmortem CSF of autopsy-confirmed patients with different distributions of pathological alphaSyn, co-pathologies, and clinical diagnoses.METHODS: alphaSyn-SAA was used to test antemortem CSF samples from 119 subjects with a variety of clinical syndromes and standardized neuropathological examinations from OHSU and UCSD (56 additional postmortem CSF samples available). The alphaSyn-SAA was also applied to frontal cortex and amygdala homogenates. Sensitivity and specificity were compared across distributions of alphaSyn-pathology. Clinical data and co-pathologies were compared across alphaSyn-SAA positive and negative groups.RESULTS: Fifty-three individuals without and 66 with alphaSyn-pathology (neocortical (n=38), limbic (n=7), and amygdala-predominant (n=21)) were included. There was a sensitivity of 97.8% and specificity of 98.1% of the alphaSyn-SAA to identify patients with limbic/neocortical pathology from antemortem CSF. Sensitivity to detect amygdala-predominant pathology was only 14.3%. Postmortem CSF and brain tissue alphaSyn-SAA analyses also showed higher assay positivity in samples from limbic/neocortical cases.INTERPRETATION: CSF alphaSyn-SAA reliably identifies alphaSyn seeds in patients with diffuse alphaSyn-pathology in the context of co-pathology and non-LBD diagnoses. The analysis of brain homogenates suggests that pathological alphaSyn in amygdala might differ from pathological alphaSyn in frontal cortex. alphaSyn-SAA might facilitate the differential diagnosis of dementias with mixed pathologies. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/ana.26453
View details for PubMedID 35808984
- Limited proteolysis-mass spectrometry reveals aging-associated changes in cerebrospinal fluid protein abundances and structures (vol 2, pg 379, 2022) NATURE AGING 2022; 2 (5): 455
Limited proteolysis–mass spectrometry reveals aging-associated changes in cerebrospinal fluid protein abundances and structures
View details for DOI 10.1038/s43587-022-00196-x
- Plasma Biomarkers of Tau and Neurodegeneration During Major Cardiac and Noncardiac Surgery. JAMA neurology 2021
Association of CSF Biomarkers with Hippocampal-dependent Memory in Preclinical Alzheimer Disease.
To determine if memory tasks with demonstrated sensitivity to hippocampal function can detect variance related to preclinical Alzheimer's disease (AD) biomarkers, we examined associations between performance in three memory tasks and CSF Aβ42/Aβ40 and p-tau181 in cognitively unimpaired older adults (CU).CU enrolled in the Stanford Aging and Memory Study (N=153; age 68.78 ± 5.81 yrs; 94 female) completed a lumbar puncture and memory assessments. CSF Aβ42, Aβ40, and phosopho-tau181 (p-tau181) were measured with the automated Lumipulse G system in a single-batch analysis. Episodic memory was assayed using a standardized delayed recall composite, paired associate (word-picture) cued recall, and a mnemonic discrimination task that involves discrimination between studied 'target' objects, novel 'foil' objects, and perceptually similar 'lure' objects. Analyses examined cross-sectional relationships between memory performance, age, and CSF measures, controlling for sex and education.Age and lower Aβ42/Aβ40 were independently associated with elevated p-tau181. Age, Aβ42/Aβ40, and p-tau181 were each associated with a) poorer associative memory and b) diminished improvement in mnemonic discrimination performance across levels of decreased task difficulty (i.e., target-lure similarity). P-tau mediated the effect of Aβ42/Aβ40 on memory. Relationships between CSF proteins and delayed recall were similar but non-significant. CSF Aβ42 was not significantly associated with p-tau181 or memory.Tests designed to tax hippocampal function are sensitive to subtle individual differences in memory among CU, and correlate with early AD-associated biomarker changes in CSF. These tests may offer utility for identifying cognitively unimpaired older adults with preclinical AD pathology.
View details for DOI 10.1212/WNL.0000000000011477
View details for PubMedID 33408146
- TAM-ping down amyloid in Alzheimer's disease. Nature immunology 2021
TREM1-PET imaging of pro-inflammatory myeloid cells distinguishes active disease from remission in Multiple Sclerosis
SOC NUCLEAR MEDICINE INC. 2020
View details for Web of Science ID 000568290500179
Soluble TREM2 is elevated in Parkinson's disease subgroups with increased CSF tau.
Brain : a journal of neurology
Parkinson's disease is the second most common neurodegenerative disease after Alzheimer's disease and affects 1% of the population above 60 years old. Although Parkinson's disease commonly manifests with motor symptoms, a majority of patients with Parkinson's disease subsequently develop cognitive impairment, which often progresses to dementia, a major cause of morbidity and disability. Parkinson's disease is characterized by α-synuclein accumulation that frequently associates with amyloid-β and tau fibrils, the hallmarks of Alzheimer's disease neuropathological changes; this co-occurrence suggests that onset of cognitive decline in Parkinson's disease may be associated with appearance of pathological amyloid-β and/or tau. Recent studies have highlighted the appearance of the soluble form of the triggering receptor expressed on myeloid cells 2 (sTREM2) receptor in CSF during development of Alzheimer's disease. Given the known association of microglial activation with advancing Parkinson's disease, we investigated whether CSF and/or plasma sTREM2 differed between CSF biomarker-defined Parkinson's disease participant subgroups. In this cross-sectional study, we examined 165 participants consisting of 17 cognitively normal elderly subjects, 45 patients with Parkinson's disease with no cognitive impairment, 86 with mild cognitive impairment, and 17 with dementia. Stratification of subjects by CSF amyloid-β and tau levels revealed that CSF sTREM2 concentrations were elevated in Parkinson's disease subgroups with a positive tau CSF biomarker signature, but not in Parkinson's disease subgroups with a positive CSF amyloid-β biomarker signature. These findings indicate that CSF sTREM2 could serve as a surrogate immune biomarker of neuronal injury in Parkinson's disease.
View details for DOI 10.1093/brain/awaa021
View details for PubMedID 32065223
NP03, a Microdose Lithium Formulation, Blunts Early Amyloid Post-Plaque Neuropathology in McGill-R-Thy1-APP Alzheimer-Like Transgenic Rats.
Journal of Alzheimer's disease : JAD
Epidemiological, preclinical, and clinical studies have suggested a role for microdose lithium in reducing Alzheimer's disease (AD) risk by modulating key mechanisms associated with AD pathology. The novel microdose lithium formulation, NP03, has disease-modifying effects in the McGill-R-Thy1-APP transgenic rat model of AD-like amyloidosis at pre-plaque stages, before frank amyloid-beta (Abeta) plaque deposition, during which Abeta is primarily intraneuronal. Here, we are interested in determining whether the positive effects of microdose lithium extend into early Abeta post-plaque stages. We administered NP03 (40mug Li/kg; 1 ml/kg body weight) to McGill-R-Thy1-APP transgenic rats for 12 weeks spanning the transition phase from plaque-free to plaque-bearing. The effect of NP03 on remote working memory was assessed using the novel object recognition task. Levels of human Abeta38, Abeta40, and Abeta42 as well as levels of pro-inflammatory mediators were measured in brain-extracts and plasma using electrochemiluminescent assays. Mature Abeta plaques were visualized with a thioflavin-S staining. Vesicular acetylcholine transporter (VAChT) bouton density and levels of chemokine (C-X-C motif) ligand 1 (CXCL1), interleukin-6 (IL-6), and 4-hydroxynonenal (4-HNE) were probed using quantitative immunohistochemistry. During the early Abeta post-plaque stage, we find that NP03 rescues functional deficits in object recognition, reduces loss of cholinergic boutons in the hippocampus, reduces levels of soluble and insoluble cortical Abeta42 and reduces hippocampal Abeta plaque number. In addition, NP03 reduces markers of neuroinflammation and cellular oxidative stress. Together these results indicate that microdose lithium NP03 is effective at later stages of amyloid pathology, after appearance of Abeta plaques.
View details for DOI 10.3233/JAD-190862
View details for PubMedID 31868669
- PGE(2) signaling via the neuronal EP2 receptor increases injury in a model of cerebral ischemia PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2019; 116 (20): 10019–24
Peripheral TREM1 responses to brain and intestinal immunogens amplify stroke severity
View details for DOI 10.1038/s41590-019-0421-2
Microdose Lithium NP03 Diminishes Pre-Plaque Oxidative Damage and Neuroinflammation in a Rat Model of Alzheimer’s-like Amyloidosis
Current Alzheimer Research
View details for DOI 10.2174/1567205015666180904154446
Intraneuronal Amyloid Beta Accumulation Disrupts Hippocampal CRTC1-Dependent Gene Expression and Cognitive Function in a Rat Model of Alzheimer Disease
2017; 27 (2): 1501-1511
In Alzheimer disease (AD), the accumulation of amyloid beta (Aβ) begins decades before cognitive symptoms and progresses from intraneuronal material to extracellular plaques. To date, however, the precise mechanism by which the early buildup of Aβ peptides leads to cognitive dysfunction remains unknown. Here, we investigate the impact of the early Aβ accumulation on temporal and frontal lobe dysfunction. We compared the performance of McGill-R-Thy1-APP transgenic AD rats with wild-type littermate controls on a visual discrimination task using a touchscreen operant platform. Subsequently, we conducted studies to establish the biochemical and molecular basis for the behavioral alterations. It was found that the presence of intraneuronal Aβ caused a severe associative learning deficit in the AD rats. This coincided with reduced nuclear translocation and genomic occupancy of the CREB co-activator, CRTC1, and decreased production of synaptic plasticity-associated transcripts Arc, c-fos, Egr1, and Bdnf. Thus, blockade of CRTC1-dependent gene expression in the early, preplaque phase of AD-like pathology provides a molecular basis for the cognitive deficits that figure so prominently in early AD.
View details for DOI 10.1093/cercor/bhv332
View details for Web of Science ID 000397257600048
View details for PubMedCentralID PMC5378482
BACE1 inhibition by microdose lithium formulation NP03 rescues memory loss and early stage amyloid neuropathology
2017; 7: 1-10
View details for DOI 10.1038/tp.2017.169
Differential deregulation of NGF and BDNF neurotrophins in a transgenic rat model of Alzheimer's disease
Neurobiology of Disease
Evidence from human neuropathological studies indicates that the levels of the neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are compromised in Alzheimer's disease. However, the causes and temporal (pathology-dependent) evolution of these alterations are not completely understood. To elucidate these issues, we investigated the McGill-R-Thy1-APP transgenic rat, which exhibits progressive intracellular and extracellular amyloid-beta (Aβ) pathology and ensuing cognitive deficits. Neurochemical analyses revealed a differential dysregulation of NGF and BDNF transcripts and protein expression. While BDNF mRNA levels were significantly reduced at very early stages of amyloid pathology, before plaques appeared, there were no changes in NGF mRNA expression even at advanced stages. Paradoxically, the protein levels of the NGF precursor were increased. These changes in neurotrophin expression are identical to those seen during the progression of Alzheimer's disease. At advanced pathological stages, deficits in the protease cascade controlling the maturation and degradation of NGF were evident in McGill transgenic rats, in line with the paradoxical upregulation of proNGF, as seen in Alzheimer's disease, in the absence of changes in NGF mRNA. The compromise in NGF metabolism and BDNF levels was accompanied by downregulation of cortical cholinergic synapses; strengthening the evidence that neurotrophin dysregulation affects cholinergic synapses and synaptic plasticity. Our findings suggest a differential temporal deregulation of NGF and BDNF neurotrophins, whereby deficits in BDNF mRNA appear at early stages of intraneuronal Aβ pathology, before alterations in NGF metabolism and cholinergic synapse loss manifest.
View details for DOI 10.1016/j.nbd.2017.08.019
Full Reversal of Cognitive Decline in Rat Model of Alzheimer Disease
CANADIAN PSYCHOLOGICAL ASSOC. 2015: 375
View details for Web of Science ID 000369408300299
Longitudinal testing of hippocampal plasticity reveals the onset and maintenance of endogenous human Aß-induced synaptic dysfunction in individual freely behaving pre-plaque transgenic rats: rapid reversal by anti-Aß agents.
Acta neuropathologica communications
2014; 2: 175-?
Long before synaptic loss occurs in Alzheimer's disease significant harbingers of disease may be detected at the functional level. Here we examined if synaptic long-term potentiation is selectively disrupted prior to extracellular deposition of Aß in a very complete model of Alzheimer's disease amyloidosis, the McGill-R-Thy1-APP transgenic rat. Longitudinal studies in freely behaving animals revealed an age-dependent, relatively rapid-onset and persistent inhibition of long-term potentiation without a change in baseline synaptic transmission in the CA1 area of the hippocampus. Thus the ability of a standard 200 Hz conditioning protocol to induce significant NMDA receptor-dependent short- and long-term potentiation was lost at about 3.5 months of age and this deficit persisted for at least another 2-3 months, when plaques start to appear. Consistent with in vitro evidence for a causal role of a selective reduction in NMDA receptor-mediated synaptic currents, the deficit in synaptic plasticity in vivo was associated with a reduction in the synaptic burst response to the conditioning stimulation and was overcome using stronger 400 Hz stimulation. Moreover, intracerebroventricular treatment for 3 days with an N-terminally directed monoclonal anti- human Aß antibody, McSA1, transiently reversed the impairment of synaptic plasticity. Similar brief treatment with the BACE1 inhibitor LY2886721 or the γ-secretase inhibitor MRK-560 was found to have a comparable short-lived ameliorative effect when tracked in individual rats. These findings provide strong evidence that endogenously generated human Aß selectively disrupts the induction of long-term potentiation in a manner that enables potential therapeutic options to be assessed longitudinally at the pre-plaque stage of Alzheimer's disease amyloidosis.
View details for DOI 10.1186/s40478-014-0175-x
View details for PubMedID 25540024
View details for PubMedCentralID PMC4293804
Neurovascular architecture following monocular deprivation in monkey primary visual cortex
CANADIAN PSYCHOLOGICAL ASSOC. 2010: 310
View details for Web of Science ID 000285987800169